Tag Archives: methane

The lakes and seas of Titan

Chapter 8 of the book “Alien Seas” presents the current understanding of Titan’s lakes and seas after the Huygens and Cassini missions.

Bodies of liquid on Titan are identified from their morphology and their radar reflection properties. The liquid on Titan is not water but a mixture of methane (CH4) and ethane (C2H6). In Chapter 4 of Alien Skies, we considered the seas of Titan in their relation with the atmosphere.

In Alien Seas we learn that the largest sea of Titan, beautifully named Kraken Mare, is about the size of the Black Sea. Titan has other large seas, and a large number of smaller lakes. The seas have rugged shorelines with fjord-like edges, typical of rapidly changing levels, suggesting that seasonal variations in methane rainfall and evaporation constantly change their size. Some seas have indeed been observed to vary in shape during the Cassini mission itself (see receding shorelines on Titan).

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The smaller lakes have more rounded shapes than the seas, reminiscent of “karstic” lakes on Earth, i.e. lakes were water sinks into the underground.

Titan’s seas are thought to consist of a mixture of ethane and methane (present measurements do not allow us to measure their composition), but the balance of the two components will depend on how much liquid sinks into the ground.

Lakes on Titan, radar image [NASA/JPL]